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No, it's... Oh, ok, it is. The only difference between this and a Death Star is the crunchy center, and a lack of soldiers in white uniforms that can't shoot straight.

I don't think it would ever be built, simply because it's exactly a space based weapon. Aim the beam at a receiving station, and everything is fine. Aim it at a major city, and... well, it won't go very well for anyone there. They say 2 technologies, laser and microwave. We know what happens to things in a residentia

Yes, I don't however see any data on their website about how wide they are planning to build the ring out. If their graphical renderings are accurate, they display a 195 pixel moon with a 22 pixel ring. Given that google tells me the moon's radius is 1737 km, that means the ring should be about 200 km wide.

The moon has an area of 37,932,000 square km though, so if we coated the entire moon and got energy from the sunny side and do the same math we get 19.34 terrawats. So, at our current state of energy usage it could power the world if we coated the moon in solar panels.

I'm not sure about the aesthetics of it though, a racing stripe on the moon.

I wouldn't trust that estimate. That's all of 1.2W/m^2. Solar radiation at our average orbit is more than 1000x that. Silicon and GaAs panels would be 200-300W/m^2. Even thin film panels should be in the several tens of watts. Remember, there's no atmospheric dissipation, nor any issues with weather. All you have to worry about are eclipses, micrometeorite damage, and radiation damage. Better have enough storage capacity to hold you over during those eclipses.

Now, that's before we cut it in half (because half the moon will be in darkness), lop off 20% for losses and partially-shady cells (due to angle, not obstacles), and we get ~77.8 terawatts. Oh, and there's one more trick: heat. Heat causes inefficiencies in a solar cell, though a design with radiators on the shady side of the panel can alleviate that fairly well (they do this in space-bound solar panels all the time).

We have had ~20 lunar eclipses so far this century. for a total of about 15 hours of total eclipse (four or five times that of partial eclipse).

So, 14 years at 8766 hours per year is 122724 hours, less the (worst case assumption - a partial hour is a total loss of power) 90 hours (worst case) of eclipse, means we've lost a potential 0.075% of the total to eclipses.

A slightly more reasonable assumption is 52 hours lost in that time, or 0.04% of our power.

I'd imagine it would be easier to have large power storage facilities at the receiving stations on Earth than to set up the long-range energy transmission system required to pipe all the electricity from the moon-facing side of Earth to the other side anyway.

All is good and all that, except for the energy input required to produce the solar cells.

Assuming we produce the solar cells here, at the bottom of the gravity well, and transport them to the moon - even if we do not include the energy required to transport that much solar cells to the moon - the energy requirement in the production of the solar cells itself would further deplete the fosiil fuels that are left on Planet Earth.

GGP talked about the possibility of coating the entire surface of the moon

Most of the energy would be spent towards keeping the furnaces lit for the crystallization process [wikipedia.org] - the rest is fairly straightforward manufacturing, and each cell by itself weighs about as much as two sheets of paper cut to the equivalent size (and is only about as thick as one sheet of paper). Brittle as hell, though...

Overall, you could launch enough (and facilities) to the Moon to get things started, then manufacture the hell out of them up there. The Moon has more than enough silicon and other needed

The factoid I remember (from I don't know where) is that 400x400 miles of "off the shelf photovoltaics" in the Arizona desert would provide enough electricity to cover the entire planet's current consumption (neglecting transmittion loss and other practicalities of having it all in one place).

I've often thought about that.... we have 3 major desert areas on earth... each about 120 apart... The American southwest, Australian outback and the Sahara. If we built a solar station on each of these three deserts, at any time, two would be producing power. A DC intercontinental power grid and we'd solve our energy problems.

You got your units wrong here, I'm afraid. The source you are referring to is not speaking about 1.2 MW per square km. It is speaking about 1.2 MW per km of road. Roads are pretty thin, so installing solar panels along them does not result in many square kilometers per km.

This mistake leads to your result being off by a huge amount. The solar constant is 1.361 GW per square km. Normally this is reduced by 30% by the atmosphere, but that does not apply in space. Neither are there clouds to worry about, so we can pretty much use this number directly, after dividing by pi to account for the lunar day/night cycle, giving us about 0.45 GW per square km. High-end satellite solar cells get up to 29% efficiency. Using that, we get 0.13 GW per square km. With an area of 11,000 km by 200 km = 2.2 million square km (we have already taken the night into account in our numbers), that results in a total production of 286 TW, which is 19 times the world's current total energy use. Of course, one has to get this energy down to earth somehow too. This seems to have an efficiency of about 85% (possibly squared - unclear) [wikipedia.org]. That partially negates the advantage of being outside the atmosphere, but we still end up receiving 206-243 TW.

So no, the main objection to this plan isn't that there wouldn't be enough energy available. It is how much resources would be spent making it. I think one will need some sort of self-replicating solar-cell-producing robot on the moon to avoid this requiring too many launches. But I have not read the tehcnical details of their plan.

Yes, I don't however see any data on their website about how wide they are planning to build the ring out. If their graphical renderings are accurate, they display a 195 pixel moon with a 22 pixel ring. Given that google tells me the moon's radius is 1737 km, that means the ring should be about 200 km wide.

So considering that we have a 11,000 km ring that is 200 km width, the power generation for the light-facing half should be what you'd expect from 5500km x 200km or 1,100,000 square kilometers. I've se [slashdot.org]

Collect massive amounts of power, and beam it towards a planet. What could possibly go wrong?

If you think people are nuts about global warming now...

Global warming is not caused by adding heat, but by changing the rate of heating, or dh/dt.Putting solar panels on the moon seems silly. They would collect twice the energy if they were placed in orbit. According to TFA, the materials would come from earth, so why go to extra effort to take them down to the lunar surface, halving their effectiveness? Also, what happens when there is a lunar eclipse?

It doesn't matter. If you have a thousand orbiting panels, and ONE is blocked by the sun, then you still get 99.9% of your power. But if you put them ALL on the moon, then during a lunar eclipse, you get close to 0%. Which means it cannot be used for base load power. Putting the panels on the moon makes no sense at all.

I think his theory is that at any time, only half of the moon is in sunshine, whereas if the panels were in orbit they could be placed to always be in sunshine. It seems to me that having them on the moon might (emphasis on might) make maintenance somewhat easier, and as long as there's enough panel area in the lit half, it's good enough, but as he says paying for both a lit half and an unlit half adds up.

First, I'm not sure what to think about the climate change political debate (which has so thoroughly obscured good science through funding bias - in both directions - and social pressure as to make actual scientific discussion practically impossible). So I'm only going to parrot for a bit.

It is all about heat, both change AND absolute. The planet is a complex system that deals with fluctuating carbon quite nicely. But those subsystems only operate well at particular temperatures. As the absolu

They would collect twice the energy if they were placed in orbit. According to TFA, the materials would come from earth, so why go to extra effort to take them down to the lunar surface, halving their effectiveness?

More like three times as effective in orbit.

On the other hand, once you get reach the point of making the structural elements from lunar aluminium, you reduce the amount of material to be lifted from Earth.

I think the article is mistaken, or at least very, very badly phrased. Perhaps "Earthly materials" was a mistranslation of "common materials"? Even TFA says water won't be taken to the moon for construction, instead only hydrogen which will be reacted with lunar oxygen to produce water. And if they need water for construction... well presumably they're talking full on manufacturing. The video offers no useful insights either.

Right on with the global warming bit - for (minimal) added reference I tracked down the numbers a while back, and IIRC the incremental greenhouse effect of one year's fossil fuel CO2 emissions is responsible for trapping something like millions of times as much energy as was contained in the fuel. And that's just in the first year, it will continue to do the same for many decades to come until eventually recaptured by the carbon cycle.

Putting solar panels on the moon seems silly. They would collect twice the energy if they were placed in orbit.

I'm not sure about the factor of 2. In earth orbit, you'd still have at least some satellites being eclipsed by the earth on a regular basis.

Perhaps it's better to put them at earth-sun lagrangian points. [wikipedia.org] They'd still be eclipsed by the moon occasionally, but only parts of the earth would be blocked at any moment during the event. Of course, you'd need to burn more fuel to get there, and additional fuel consumption to maintain the lagrangian orbits would cut down on the useful lifetime of the satellites.

Solar insolation on the moon is not dramatically higher than on Earth - around 1400 W/m^2 versus around 1000 W/m^2 on Earth. Granted, a Lunar solar station wouldn't be affected by weather, but Earth based receivers will suffer from efficiency loss during bad weather.

Could they achieve the same result by building a bit larger system on earth, but without the hundreds (or thousands?) of rocket launches it would take to get the materials to the moon to get the thing started?

Solar insolation on the moon is not dramatically higher than on Earth - around 1400 W/m^2 versus around 1000 W/m^2 on Earth. Granted, a Lunar solar station wouldn't be affected by weather, but Earth based receivers will suffer from efficiency loss during bad weather.

Could they achieve the same result by building a bit larger system on earth, but without the hundreds (or thousands?) of rocket launches it would take to get the materials to the moon to get the thing started?

Besides, who wants to see a big black ribbon around the moon?

They plan to use lunar materials, so no hundresds of rocket launches to get started. I guess the point is kind of that real estate and raw materials are "free", if you get the proper manufacturing equipment up there. If that equipment is automated enough, you can build up slowly, but steadily.

I think you are under estimating the amount of machinery it takes to turn a mountain of rock, dirt, and minerals into a field of solar panels. The infrastructure required for that would likely eclipse the 11,000 KM stripe of solar panels.If you wanted to manufacture sophisticated stuff like that on the moon, you would need it to be as the last step of a 200 year plan to start mining/industry/living on the moon.

If you wanted to manufacture sophisticated stuff like that on the moon, you would need it to be as the last step of a 200 year plan to start mining/industry/living on the moon.

Let's do THAT. And build the world-girdling strip of solar panels, all tied together with superconductors (easy to use, on the Moon), and use that power on the Moon for the burdgeoning civilization we're building there. Forget beaming it at Earth.

The "burgeneoning civilization" on the moon includes a bunch of junk from the 1970s, a few crashed probes and a half functioning Chinese probe who's largest scientific advance has been to tweet badly translated anthropomorphic homilies.

We have yet to manufacture a condom on the moon, much less complex semiconductor devices.

If we are going to dream big: build a space elevator, space fountain, or a launch loop first. After the cost of getting something into orbit drops by several orders of magnitude everything else gets easier.

Solar insolation on the moon is not dramatically higher than on Earth - around 1400 W/m^2 versus around 1000 W/m^2 on Earth. Granted, a Lunar solar station wouldn't be affected by weather, but Earth based receivers will suffer from efficiency loss during bad weather.

Could they achieve the same result by building a bit larger system on earth, but without the hundreds (or thousands?) of rocket launches it would take to get the materials to the moon to get the thing started?

Besides, who wants to see a big black ribbon around the moon?

They plan to use lunar materials, so no hundresds of rocket launches to get started. I guess the point is kind of that real estate and raw materials are "free", if you get the proper manufacturing equipment up there. If that equipment is automated enough, you can build up slowly, but steadily.

That's why I started at the low end of "hundreds of launches" -- if raw materials were needed, launches would be in the many thousands or tens of thousands. Unless aliens left us a manufacturing plant on the moon when they buried the monolith [youtube.com], it's going to take a lot of equipment to get started.

Construction of the ISS required over 40 assembly launches. [seds.org]. And those launches were all to LEO which allows much bigger payloads than launching to the moon.

Strategic Defense Initiative (Star Wars) http://en.wikipedia.org/wiki/S... [wikipedia.org]
The US contractors and gov spend time and treasure looking at different forms energy over distance in space.
Something very expected happens over distance to all that power, then add in the earths weather and you have non trivial issues.
Add ever more power or lasers or wavelengths... it all drops off fast but finding out just how and by how much can be a wonderful boondoggle.
Interaction of multiple lasers, different rays, microwav

A major issue is that the moon is fairly far up Earth's gravity well. It is easy to get things to low-Earth orbit and already tough to get things to even geo-stationary. The main saving of putting anything on the moon will come if you can do a large part of your construction on-site since otherwise moving that much material up is going to be tough. If you are doing automated construction on site you also are going to need to be able to make mainly a lot of solar cells. Solar cells are primarily silicon and there's already been prior research on refining the moon's regolith for silicon to manufacture electronic components and that looks possibly doable but one does need to get over some technical chemistry issues. See e.g. http://www.asi.org/adb/02/13/02/silicon-production.html [asi.org].

The other issue is distance for power transmission: most designs for microwave power involve power transmission from at most a little over geo-stat at about 35,000 km. The distance to the moon is about 10 times that, so if you don't have a really tight beam, there are going to be issues. Also, since the moon change's position you are going to need a large number of sites on Earth that can receive the beam, and if you can't switch off smoothly between them always (which would itself require massive planet-wide infrastructure), you would still need power sources on Earth (possibly just massive storage facilities?) to deal with those times.

Overall, a really cool idea with a lot of technical hurdles. I hope they can make it work but I'm not optimistic.

Ok. I just looked at their plan in more detail (that is read all of TFA). They are planning on getting the solar panels and most other infrastructure from Earth. That means massive costs in terms of riding up the gravity well. This makes their plan look extremely implausible.

Go to the company website instead. They say lunar resources and are able to tell the difference between kms and miles. However, it's all a bit pie in the sky even there. Even with the advantage of lunar resources, I would be more optimistic about geostationary orbital solar power. Microgravity would mean that you could get away with really thin structures, even concentrated thermal solar might make sense if you can work out a reasonable cooling part of the cycle (just make an extremely thin mirror as the bu

I suspect cooling would be a much larger challenge on the moon - no fluids to transport environmental heat away, so you're limited to dumping it into the rock (how fast can heat conduct through lunar rock?) or radiating into space. Plus the whole "moving parts need maintenance" issue is going to be a lot harder to deal with on the moon.

The concentrated solar is a good idea though, no reason it couldn't be combined with photovoltaics instead. With no winds to deal with you could potentially just use a thin

Don't you all think this is a bit premature? We haven't built anything on the moon. The closest we've come is a giant multigoverment, multidecade effort to keep a bunch of cylinders in low earth orbit. We've managed to grow a few beans and worms, but haven't even assembled a Heath kit in orbit.

Doesn't seem very plausible to expect a company with unknown funding and absolutely no real world experience to run rings around everyone else's best efforts.

Also, since the moon change's position you are going to need a large number of sites on Earth that can receive the beam, and if you can't switch off smoothly between them always (which would itself require massive planet-wide infrastructure), you would still need power sources on Earth (possibly just massive storage facilities?) to deal with those times.

That is funny. If you have massive storage facilities, preferably extremely cheap and relatively innocuous to the environment, then you've solved the whole electrical power problem already. Current wind and solar generation are atrocious because of the lack of such storage.

That's a good point, so from a strict get-there-once attitude this won't be so bad. However, I don't think that slamming into the moon is going to be a good strategy here unless they used some sort of extremely robust system which would create its own problems.

Perhaps they should focus on one incredibly ambitions plan instead of eight separate ones. I'm also a bit curious how big the receivers would have to be earthside to collect the beamed energy. I don't know if they've invented the microwave equivalent of a laser which is probably what would be needed to to keep the receivers less than 20 miles wide.

Because the distinction between a targetable multi-terawatt laser and an eco-friendly solar-power downlink is mythical (legal, at best). So Japan can bypass (simultaneously, no less) their own constitutional ban on militarisation AND the internal treaty against "space weapons".

Actually, lunar-based solar power for Earth is decades old, and was first patented [google.com] by Dr. David R. Criswell [lunarsolarpower.org] in the late 80s. I was working for Dr. Criswell at the California Space Institute in La Jolla in 1985 while he was developing this idea so I know it goes back at least to the mid 80s.

Shimizu Corporation intersects with Dr. Criswell in another way that I just discovered today after searching for his more recent patents.

We've got to attract technological civilization's population away from natural ecosystems into idealized artificial environments such as Shimizu Corporation's design for what it calls the "Green Float" [shimz.co.jp]. You can house the entire population of civilization in beach-front property on the boundary of a tropical rain forest where people can swim, fish, hunt and gather recreationally, as well as access the height of urban lifestyle. From there space habitats are likely to emerge so that the natural propensity of these "cells" to replicate endlessly needn't destroy Earth's biosphere. Interestingly, I came up with a geometry that looks very similar to that years ago, with the Solar Updraft Tower Algae Biosphere proforma [oocities.org] and, over the subsequent years, I found a floating photobioreactor technology that requires little more than 2 layers of polyfilm that has demonstrated production per cost figures far in excess of what I projected in that proforma. Before I ran across Shimizu Corp's Green Float I had further refined the idea based on the Atmospheric Vortex Engine [blogspot.com], which, like Shimizu's "Green Float", is ideally sited in the equatorial doldrums and could make use of the central tower of the Green Float. I posted some preliminary thoughts over at the Seastead Institute's blog [seasteading.org].

A key problem I attempted to address in my preliminary thoughts was the early market for energy from the Atmospheric Vortex Engines that would form the nuclei for Shimizu's Green Floats. A big problem was the fact that the electric power markets are thousands of miles away from the floating AVEs even if you could build on the order of a terawatt of oceanic power transmission lines thousands of miles long. Early markets are critical for attracting capital -- the lack of which renders such grandiose ideas "non-starters".

I had thought it would be very nice to have a microwave transmission technology that could dynamically switch the power distribution to achieve the holy grail of "dispatchable [wikipedia.org]" power generation for peak loads, but wasn't aware, until just now, that Dr. Criswell's recent revision of his patent [google.com] serves precisely that purpose.

I remember having this conversation in Physics class many years ago, would be fantastic if it goes ahead but I honestly don't think that anyone would invest the huge amount of money needed to even attempt this, at least not until the oil has run out.

I would say that only the Japanese would think surface area here on Earth to be at such a premium that it would be worth it versus panels here on Earth.

I would, except for the slew of other people who have proposed lifting them into orbit.

I view all such proposals as a distraction from the real logistics issues involved in installing more of the renewables we can build now and connect to the power grid by more conventional means, with the added whimsical notion that what they really want is a death ray.

> I view all such proposals as a distraction...So do I for the most part - but maybe not for Japan. After all they don't really have the land area to do much in the way of renewables themselves, are subject to tropical storms which make offshore source problematic, and they aren't exactly on the best terms with their neighbors.

Plus there's the fact that such a system could very easily be modified into a terrifying weapon, which could do a great deal for the national security of a tiny island nation off

This proposal would only make sense if you planned on using the first few missions to establish the ability to turn local Lunar resources into solar panels

On the other hand, an orbital system would have to lift well... how much?

current solar panels weigh 15.8 kg/m^2, lets make life simple and imagine that they can make solar panels that are 1kg/m^2and the moons equator is 11,000 Km (I can;t believe that the story said that it was miles...) and lets say they decide to make it a Km wide that is11 billion kg o

The problem is not peak oil, but peak affordable oil.We are already there, the big oil companies have cut back exploration because the cannot make money even at $100/barrel.High oil prices choke off growth in our economyWith little or no growth, we cannot pay our debts.As in 2008, unpayable debt will crack our financial systemAs not in 2008, the central banks have shot most of their “arrows” and have few left in their quiver.With a broken financial system, we will have the social chaos that was barely avoided in 2008

Actually the problem is that Earth-based solar collection is terribly inefficient. A solar cell (15 - 20% efficient to begin with), fixed to one spot on the Earth, is exposed to sunlight for a fraction of a day, sunlight which has been diffused by the Earth's atmosphere.
Extraplanetary collection is actually a very good idea.

The moon is tide-locked to the Earth, not to the sun. The so-called "dark side of the moon" gets just as much sunlight, but it never faces us. Moon based solar collection will have most of the problems that Earth based collection has... and a whole host of new problems.

So the 10% or so that are actually working will get light half the time. Right.

Has everybody forgotten what the lifespan of your average photovoltaic cell is? They'll burn out faster than we can replace them - I mean, that's a lot of solar cells, guys. I seriously doubt that Alpha can keep up with just the replacements, let alone completing the original design.

It's not the energy we use that does the warming - the CO2 released from burning fossil fuels captures about a million times as much solar energy per year as there was energy in the fuel, and it does so for many decades before leaving the atmosphere.

The point being, if we get the same amount of energy from lunar solar as from fossil fuels, we'll cut our influence on warming a million-fold, at which point it becomes a non-issue. And we'd be doing so without even any of the environmental impacts of terrestrial renewables.